1. Field of The Invention
This invention relates to fiber reinforced silicon carbide ceramics, and more particularly to fiber reinforced silicon carbide ceramics having improved strength and toughness and suitability as a heat-resistant structural material, wherein heat-resistant inorganic short fibers having no damage are three-dimensionally and uniformly dispersed into a matrix composed of silicon carbide to form a shaped body containing these heat-resistant inorganic short fibers entangled with each other, as well as a method of producing the same.
2. Description of Relevant Materials
As a new application of the ceramic, it has recently been examined for use in heat-resistant structural materials and materials for bio hard texture. In such applications, however, there is a basic problem in that the ceramics lack strength and toughness.
Heretofore, fiber reinforced ceramics obtained by adding fibers to the ceramic, has been proposed for overcoming this problem. For example, Al.sub.2 O.sub.3 -SiC whisker composite material is known as a typical fiber reinforced ceramic. The mechanical properties of such a composite material are fully discussed in a study by Matsubara, Okuno, Watanabe, Matsuo et al. (Association of Japan Ceramics, the abstract collection for 7th basic forum of high temperature material, pp. 14.about.19).
Further, a method of producing ceramic composite materials by reinforcing silicon carbide ceramic with fibers has been proposed in Japanese Patent laid open No. 52-81309, Japanese Patent laid open No. 58-145668 and Japanese Patent laid open No. 62-12671. Also various "ceramic fiber reinforced ceramics" have been disclosed in "Toyota Central Res. & Develop. Labs., R & D Review" (vol. 20, No. 3/4 1986).
In the aforementioned conventional techniques, ceramics having somewhat improved toughness are obtained. However, there are not yet developed fiber reinforced ceramics satisfying conditions required of a structural material or a material with bio hard texture such as artificial bone or artificial tooth root, i.e. ceramics having excellent toughness and strength.
In the fiber reinforced ceramics produced by these conventional techniques, the green body is shaped using a dry shaping method, or the relatively low-density green shaped body is highly densified by pressure sintering, so that the heat-resistant inorganic fibers such as whickers or the like are considerably deformed or even broken in an extreme case. As a result, the toughness and the strength are not so improved though the heat-resistant inorganic fibers are compositely added.
Further, in the above conventional technique, there is a tendency for the heat-resistant inorganic fibers to be oriented in a two-dimensional direction, so that anisotropy is caused in the strength and consequently there is a problem in that the anisotropy should be considered in use of the ceramics.
An object of the invention is to solve and overcome the problems inherent in the known fiber reinforced ceramics, among the various problems in the aforementioned ceramic reinforcing techniques.